Quantum chemical methods for the calculation of indirect NMR spin–spin coupling constants
and chemical shifts are always in progress. They never stay the same due to permanently …

This article primarily discusses the utility of vibrational perturbation theory for the prediction
of X–H stretching vibrations with particular focus on the specific variant, second-order …

Every attempt to employ mathematical methods in the study of chemical questions must be
considered profoundly irrational and contrary to the spirit of chemistry. If mathematical …

We review our development on beyond Born–Oppenheimer (BBO) theory and its
implementation on various models and realistic molecular processes as carried out over the …

Since its introduction into quantum chemistry in the late 1960s by Cizek and Paldusf “3
coupled cluster theory has emerged as perhaps the most reliable, yet computationally …

Consider a system with an arbitrary constraint on its electron density (eg, that there are N
charges on a certain group of atoms). We show that in Kohn-Sham density functional theory …

Planar (D 6 h) benzene has one (1181 i cm-1, b 2g) and three (1844 i cm-1, b 2g; 462 i cm-
1, e 2u) imaginary vibrational frequencies at the MP2/6-311++ G (d, p) and MP2/6-311++ G …

We describe an alternative procedure for obtaining approximate Brueckner orbitals in ab
initio electronic structure theory. Whereas approximate Brueckner orbitals have traditionally …

The model Hamiltonian approach of Köppel et al [Adv. Chem. Phys. 57, 59 (1984)] is used to
analyze the electronic spectroscopy of the nitrate radical (NO 3)⁠. Simulations of negative …

Using a Lagrangian-based approach, we present a more elegant derivation of the equations
necessary for the variational optimization of the molecular orbitals (MOs) for the coupled …